Melancon, who has a solid resume for a previous stint in the National League with the Astros, immediately becomes a main man in the back of the bullpen. He could draw on past closing experience to replace Hanrahan, or be a leading candidate to set up if Jason Grilli assumes the closer's role. De Jesus, the 25-year-old son of the 15-year Major League veteran, provides infield depth.

Prospect acquired by Pirates

Stolmy Pimentel, RHP: Pimentel began the 2012 season ranked No. 14 on the Red Sox's Top 20, but he has seen his star fade over the past two seasons as he had difficulty making the leap to Double-A. He'll be just 23 for all of the 2013 season, so there's still time for him to turn things around. It appeared like Pimental may have been doing that in the second half of 2012, posting a 3.17 ERA and a .207 batting average against in 10 starts after the All-Star break. He still has the makings of a very good three-pitch mix, with a fastball that can be plus at times, an outstanding changeup and an average breaking ball. Pimental has struggled with command in the past, both in and out of the strike zone, with some thinking he was destined for a bullpen role as a result. If his second half wasn't an aberration, then the potential for him to become a solid big league starter still exists. That might be exactly what the Pirates are banking on.

Sands, who also plays first base, made a solid debut with the Dodgers in 2011 and was acquired by Boston in the October completion of the midseason blockbuster between the teams that involved Adrian Gonzalez, Carl Crawford and Josh Beckett.

Sands, 25, could very well be viewed as the long-range key to the trade from the Pirates' perspective. The 6-foot-4, 225-pound right-handed hitter has produced 119 home runs in 469 Minor League games, and he drove in 26 runs during a 61-game big league baptismal in 2011.

"Jerry Sands has impressed our scouts with his well-rounded tools package, highlighted by his ability to command the strike zone as a hitter and drive the ball for extra-base hit potential," Pittsburgh general manager Neal Huntington said upon announcement of the deal. "Additionally, his defensive versatility will increase his opportunity to contribute to [us] in the near term as well as in the years to come."

Melancon, 27, answers some of the attrition of the Bucs' bullpen since the start of the 2012 season. Hanrahan tops the exodus that began with the midseason trade of Brad Lincoln, continued with the release of veteran Juan Cruz and included Chris Resop's trade to Oakland in November.

Originally drafted (ninth round in 2006) and signed by the Yankees, Melancon made his brief big league debut with the Bombers in 2009. In New York and in Boston, he put up an ERA of 5.79 in 56 games. However, in between, he appeared in 91 games for Houston and went 10-4 with a 2.85 ERA. As the Astros' primary closer in 2011, he converted 20 of 25 save opportunities.

"Mark Melancon has been a quality Major League reliever with closing experience who displays key subjective and objective indicators as a candidate to bounce back from a challenging 2012 season," Huntington said. "Similar to when we acquired Joel Hanrahan [in 2009, from the Nationals], our scouts saw a quality pitch package that was not accurately reflected by his present level of performance. Mark will be a solid addition to our bullpen."

Reached in Hawaii by MLB.com, Melancon already looked forward to a return to the NL and to possibly closing. He expected that subject to arise later Wednesday, during his first conversation with manager Clint Hurdle and Huntington.

"It's a lot different strategy and pitching changes and stuff you've got to account for," Melancon said of NL ball. "I feel like it's more true baseball and better baseball, but I'm sure the hitters don't agree with me.

"For sure," he added, about wanting a chance to close. "I do have that experience. I feel like I'm pretty good at doing that. If need be, I could step in and help the team."

Pimentel, a 22-year-old native of the Dominican Republic, was 6-7 with a 4.59 ERA in 22 starts for Double-A Portland in 2012, his sixth season in Boston's farm system.

De Jesus, drafted by the Dodgers and their Minor League Player of the Year in 2008, is a career .298 hitter in 729 games in the Minors. His big league experience consists of 73 at-bats.

Hanrahan, the extremely popular and effective right-hander, moves on after converting 82 of 94 save opportunities in his 2 1/2 seasons as the Bucs' closer. The two-time All-Star is on target to earn about $7 million in his final go at salary arbitration, and the Pirates had to seek alternatives to locking up 10 percent of their anticipated $70 million payroll in a reliever.

"Trading Joel Hanrahan was a difficult decision," Huntington said. "But we are pleased that the direct result will be the addition of three players who will very likely impact our Major League club this season, plus a pitcher who will add to our deep and talented pitching prospect base."

Holt was an instant sensation late last season when he stepped in at second base after Neil Walker was shelved by a herniated disk in his lower back. Holt hit safely in nine of his first 10 big league starts (16-for-44), and overall he batted .292 in 24 games and 65 at-bats.

Melancon, Pimentel and Sands immediately went on the Bucs' 40-man roster, maxing it out. A move was expected later on Wednesday to clear room for De Jesus.

Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. Evan Drellich contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.